1. Field of the Invention
The present invention relates to an image forming apparatus comprising, a laser scan unit that forms a latent image on a surface of a photoconductor drum by irradiating laser beams while scanning.
2. Description of the Related Art
In a conventional image forming apparatus such as a laser beam printer that utilizes electrophotographic technology, an optical system for scanning laser beams is unitized as a laser scan unit in consideration of workability of assembly or easiness of maintenance. Such a laser scan unit is previously adjusted to have a predetermined quality when components thereof are assembled as a unit. Thus, it is no need to adjust the laser scan unit after the assembly, so that it can be handled as a component, that is, a black box.
As for the attachment of the laser scan unit on the image forming apparatus, the laser scan unit is generally fixed on a metal frame provided inside the image forming apparatus by screws. In addition, it is necessary to adjust the position and posture of the laser scan unit so that a main scanning direction of the laser beam by the laser scan unit becomes perpendicular to a sub-scanning direction (paper feed direction) of a paper sheet by a paper feed mechanism when the laser scan unit is fixed on the frame of the e image forming apparatus. Therefore, various arts are conventionally proposed with respect to installation positioning control of the laser scan unit.
Japanese Laid-Open Patent Publication No. 8-11348 discloses a conventional image forming apparatus that a wedge shaped member is provided between a laser scan unit and a frame of an image forming apparatus. The laser scan unit is fixed on a plane of the wedge shaped member and the wedge shaped member with the laser scan unit is rotatable fixed on the frame around a predetermined rotation axis, so that a main scanning direction of laser beam by the laser scanning unit can be adjusted minutely. The wedge shaped member, however, becomes larger than the laser scan unit, so that it causes upsizing of the image forming apparatus. Furthermore, the wedge shaped member is necessary to be finished to a predetermined quality, so that it causes the cost rise.
Japanese Laid-Open Patent Publication No. 2000-249953 discloses a conventional image forming apparatus that four corners of a laser scan unit is fixed on a frame of an image forming apparatus, and a wedge shaped spacer is slidably provided between the laser scan unit and the frame at one corner. Inclination of the laser scan unit with respect to the frame can be adjusted by moving the spacer. It, however, needs a space to provide the spacer slidably, so that it is difficult to downsize the image forming apparatus. Furthermore, the insertion of the spacer between the laser scan unit and the frame causes the deformation of a housing of the laser scan unit.
Japanese Laid-Open Patent Publication No. 2001-125026 discloses a conventional image forming apparatus that comprises an angle adjuster of a light source in an optical system for scanning laser beam. Such a configuration, however, needs angle adjustment of the light source after attachment of the optical system for scanning laser beam on the image forming apparatus, so that it is impossible to unitize the optical system for scanning laser beam as a laser scan unit that needs no adjustment.